Optimization of an in vivo X-ray fluorescence mercury measurement system

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2004, Vol.213, p.560-563
• Main Authors: O’Meara, J.M., Börjesson, J., Chettle, D.R., McNeill, F.E.
• Format: Article
• Language: English
• Subjects: Fluorex; In vivo X-ray fluorescence; Kidney; Mercury; Polarized XRF
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(03)01670-7

A non-invasive in vivo X-ray fluorescence (XRF) method of measuring renal mercury concentrations has previously been reported, as a potential occupational monitoring tool for those who work with this toxic element [Phys. Med. Biol. 40 (1995) 413]. However, the detection limits remain high compared to the typical values anticipated in these populations. Our approach for further enhancing the XRF renal mercury detection limit has been threefold: investigations of the ideal filtration and tube voltage with a conventional tungsten anode X-ray tube, and the replacement of the existing tungsten X-ray tube with a Fluorex tube [Phys. Med. Biol. 36 (1991) 1573]. In all cases the systems were compared by Monte Carlo simulation to that reported by Börjesson et al. [Phys. Med. Biol. 40 (1995) 413]. The optimal filtration was found to be a 0.035 cm uranium filter, positioned after the polarizer. Modest improvement was achieved by increasing the tungsten tube voltage from 160 [Phys. Med. Biol. 40 (1995) 413] to 200 kV, decreasing the system detection limit by 27% for the same subject dose. It was found that the Fluorex tube did not improve the system sensitivity for a given dose rate, either when the tube was used for direct excitation or in a polarized configuration. Despite the improved performance reported here at 200 kV, detection limits remain high compared to typical levels in occupationally exposed individuals.